1. Field of the Invention
The present invention generally relates to a method and device for fluid sampling, and more particularly, to a fluid stream sampler that permits the detection and measurement of constituents of a fluid stream that is directed through the sampler and a method to capture and transport a sample of the fluid stream for subsequent analytical laboratory analysis.
2. Background of the Invention
In conventional fluid stream sampling the collection of samples for aerosol analysis of fluid (typically air) stream constituents, employing either slit impaction cassette media, micro porous filter media or inflatable gas bag media technology, was typically accomplished by fixing the media in line to a vacuum pump sized for the specific sampling event. The vacuum pump would have a air stream flow indicator and air stream flow metering regulator set in line with the air stream which could then be metered to vary the flow rate for calibration or in another variation of the prior art the pump motor speed was electrically adjusted to vary the flow rate for calibration specification and then the rate was verified by a stand alone electronic flow indicator meter, of which many varieties exist. Conventional sample media technology demands that flow rates are known so total volume sampled can be calculated to develop representative analytical data for the overall environment being tested. Additionally, sample media technology requires that optimal particulate trace dispersion on split impaction cassette media or micro porous filter media will occur if the air flow rate is regulated based on the media manufacturer's recommendations and in gas bag media technology air flow rate is regulated so as to fill the bag at a controlled rate to prevent accidental bag rupture from rapid over inflation. The conventional approach to collecting fluid stream samples is not conducive to those persons who are not highly skilled and experienced in fluid stream sampling. The operation of conventional fluid sampling devices requires, for example, prior knowledge of vacuum pump generation technology to properly size the pump to be employed as the vacuum source, as well as to properly select the properly sized air flow gauge or electronic calibrator. The operation of conventional fluid sampling devices also requires specialized knowledge as to how such devices are properly read and interpreted so as to ensure that a properly regulated flow rate is obtained from the vacuum source, as well as specialized knowledge as to how such rates optimize the particular mode of media being employed. The operation of conventional fluid sampling devices when applied to a conventional vacuum chamber to obtain a gas bag media sample also requires specialized knowledge as to how the fluid stream is properly directed to aspirate the gas bag media by differential pressure at a regulated rate according to standard operating procedures promulgated by governmental environmental regulatory bodies. Lastly, conventional fluid sampling methods often require a constituent sample media that has been employed for sampling to be returned to the laboratory for subsequent analysis. Often times the laboratory is at a great distance from the sampled source and postal shipping is required with the media being packaged as a additional event to the sampling event in distinct and independent elements, typically cardboard boxes.
The present fluid (typically air) stream sampler device with flow rate controller and indicator provides a improved variable flow rate-controlled air sampler that overcomes the shortcomings of conventional devices that employ distinct and independent elements to achieve a measurable volumetric flow rate. In accordance with the present device, the mass flow indicator in the form of a element, commonly known as a rotameter, is an element that is integral to the device, and consists of a vertical flow tube structure molded directly into the sides of the sampler shell body. Additionally, a variable damper panel is held in position by annular friction fit protrusions molded into the side of the sampler shell body to firmly stabilize the damper when moved under negative pressure flows.
The present fluid stream sampler provides an improved variable flow rate controlled air sampler in which the flow rate can be set over a wide range by a fine axial adjustment of the damper panel, flow rates being limited only by the strength of the vacuum source (conveniently a household vacuum cleaner) and calibrated by the visual indicator of a ball floating between calibration lines drawn on the window to the rotameter.
The present fluid stream sampler also provides an improved variable flow rate controlled air sampler that can be operated by persons who do not necessarily have the specialized skills and experience of persons who operate conventional devices of this type.
The present fluid stream sampler also provides an improved variable flow rate controlled air sampler in which the primary components can be concurrently formed in a injection molded process during manufacture of a thermoplastic embodiment of the fluid stream sampler.
The present fluid stream sampler also provides an improved method to obtain a fluid sample by improving a vacuum chamber gas bag fill component of the sampler which overcomes the shortcomings of conventional gas bag vacuum chamber fill component with the gas bag subcomponent requiring a rigid fill port valve element and a distinct and independent shipping container element. In accordance with the present device, the fill port valve of the gas bag subcomponent is an element that is integral to the bag, and consists of a two-ply flexible film structure which self-seals upon removal of the fill port straw. Additionally, the vacuum chamber component (conveniently a paper shipping tube) for the present fluid stream sampler serves a secondary and integral function as the protective shipping container of the gas bag which contains the fluid sample.